Centrifugal infiltration of particulate metal matrix composites : process development and fundamental studies/

A high-pressure liquid infiltration process utilizing centrifugal force was designed and laboratory equipment developed. In this process, a mold containing reinforcing materials was located at the end of an elongated runner, which was filled with a molten metal. Rotation of the runner created centrifugal force driving infiltration. To obtain high pressures, the metal head was controlled to be long and constant throughout the process. Threshold pressures required for infiltration of several packed ceramic powders were determined using the laboratory equipment built. Achievable pressures were up to 150 atm for Sn-15 wt% Pb. The pressures allowed SiC, TiC, and A1203 powders ranging in sizes from 25 [mu]m to 300 [mu]m, packed to a high volume fraction, to be infiltrated by Sn-15 wt% Pb. Threshold pressure results obtained agree well with experimental results previously reported, and with calculated values. Observations of the resulting composite structures showed layering and porosity defects. Layering defects, but no porosity defects, were observed in the composite samples containing coarse powders. In contrast, the composites containing fine powders possess porosity defects, but not layering defects. The layering defect was attributed to the depacking mechanism of the powders during the cold pressing process. The porosity defect was attributed to insufficient applied pressures. A new packing process was proposed to avoid layering in coarse powders. Macrosegregation and microsegregation were limited in all samples. The interparticle spacings of these composites were smaller than the dendrite arm spacing would have been at equivalent cooling rates; thus, dendrite formation and microsegregation were effectively suppressed.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Materials Science and Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2004

Author dc:creator

• Wannasin, Jessada, 1977-

Advisor dc:contributor.advisor

• Merton C. Flemings.

• Materials Science and Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/32267

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/32267